var _wnd_content = '
<div id="abc">
 text
</div>
';

var _wnd_content = '
  <div id="abc">
    text
  </div>';

var _wnd_content = [
    '<div id="abc">',
    '    text',
    '</div>'
].join("n");

<script type="text/x-my-template" id="template_abc">
    <div id="abc">
        text
    </div>
</script>

var _wnd_content = $("#template_abc").html();

var _wnd_content = <div id="abc">text</div>;

var _wnd_content = `
    <div id="abc">
        text
    </div>
`;